HP NC550SFP Dual Port 10GbE Server Adapter - Manual (Page 5)

Overview 5
Overview
iSCSI Overview
The Internet Small Computer System Interface (iSCSI) is an IP-based standard for linking data storage
devices over a network and transferring data by carrying SCSI commands over IP networks.
An iSCSI network consists of one or more iSCSI storage units (targets) connected through a copper or
optical networking cable to 10Gb Ethernet network switches or IP routers. To this network one or more
servers are connected, which are responsible for transferring data to or from the storage units.
When an operating system receives a request it generates the SCSI command and then sends an IP
packet over an Ethernet connection. At the receiving end, the SCSI commands are separated from the
request, and the SCSI commands and data are sent to the SCSI controller and then to the SCSI storage
device. iSCSI also returns a response to the request using the same protocol.
All storage protocols including iSCSI have two ends in the connection; the initiator and the target. In
iSCSI, they are known as the iSCSI initiator and the iSCSI target. Each server or machine directly
accessing an iSCSI target requires an iSCSI initiator. It is the initiator that allows the host system to
communicate directly with iSCSI targets.
Constructing a basic iSCSI SAN
There are three main components that make up an iSCSI SAN:
• iSCSI Targets. An iSCSI SAN has one or more iSCSI targets, which house and make available the
storage used within the SAN. The iSCSI target is the storage device itself or an appliance that
controls and serves volumes or virtual volumes. The target is the device that performs the SCSI
command or bridges it to an attached storage device. iSCSI targets can be disks, RAID arrays, or
even Fibre Channel (FC) fabrics.
• Networking infrastructure. The networking infrastructure in an iSCSI SAN uses Ethernet transport. HP
NC-Series ServerEngines uses the BladeEngine 2 controller. The configuration and complexity of the
storage network depends on its intended function and features required.
• iSCSI Initiators. The initiator allows a given machine access to the storage available in the iSCSI
SAN. It requests all SCSI operations like read or write. An initiator is usually located on the
host/server side either as hardware (iSCSI host bus adapter (HBA)) or software (iSCSI software
initiator). To transport block (SCSI) commands over the IP network, an iSCSI driver must be installed
on the iSCSI host. An iSCSI driver is included with HP NC-Series ServerEngines BE2 adapter.
Managing an iSCSI session
To transmit information from an initiator to the target, the initiator must first establish a session with the
target through an iSCSI login process. The login process:
• Starts a TCP/IP connection
• Verifies that the initiator has access to the target (authentication)